Telephone headsets worn by the user and comprising one or two receiving ear pieces and a speech transmitter, have multitudes of uses including major uses as operator and airline pilot headsets. Often, however, the use location or environment contains substantial amounts of unwanted ambient noise which interferes with the intelligibility to the user of the incoming speech.
Noise suppression circuits are found in the prior headset art which reduce or cancel the undesired noise. One method is to detect the unwanted noise, convert this from an acoustic signal to an electronic replica, create an inversion thereof which is essentially 180 degrees out of phase with the ambient noise signal and play the inverted signal into the headset's receive channel which subtractively interferes with the unwanted noise signal.
The effectiveness of suppression circuits, however, is critically dependent upon a careful design of the headset housing and its interior acoustics. For example, identification and control of acoustic paths within the headset housing are important in achieving cancellation over wide bandwidths.